Three-dimensional Vacancy Clusters Research Articles

A study of defect states in neutron-irradiated zirconium using positron annihilation spectroscopy

Positron annihilation spectroscopy has been used to examine specimens of iodide-purity zirconium, irradiated with neutrons in the temperature range 355 K to 725 K. The mean positron lifetimes and Doppler broadening lineshape parameters from the irradiated specimens showed significant increases over values for annealed material. A two-component analysis of the lifetime spectra indicated saturation trapping at vacancies and dislocations for the lower irradiation temperatures. No evidence was found for the presence of trapped components with long lifetimes (τ 300 ps), indicative of three-dimensional vacancy clusters. Recovery of the 355 K irradiation damage during annealing was interpreted in terms of the annihilation of vacancies at sinks (dislocations and grain boundaries) and recovery of the irradiation-induced dislocation structure.

The thermal annealing of heavy ion damage in copper

Abstract Dislocation loops and three-dimensional vacancy clusters are created by 150 kev Zn + bombardment. The number of vacancies in them after successive isochronal anneals is measured by electron microscopy. At 200°c annealing is thought to take place by interstitial absorption. Thereafter, dislocation loops anneal with an activation energy close to that of self-diffusion, and clusters with an energy of about 1.3 ev.